(1) Field of the Invention
The present invention relates to a half bearing for supporting a crank shaft of an internal combustion engine and to a plain bearing having two half bearings.
(2) Description of Related Art
From the past, a plain bearing constituted by a pair of half bearings has been employed as a main bearing and a connecting rod bearing. A so-called crush relief is formed in a plain bearing adjacent to mating surfaces of half bearings.
A crush relief is a wall-thickness thinner region that is formed in a region adjacent to a circumferential end surface of a half bearing such that a thickness of a wall is thinner toward the circumferential end surface. A crush relief is formed with an intention of absorbing misalignment or deformation of joint surfaces of a pair of half bearings in a state where the half bearings are assembled (see, for example, JP-A-4-219521 and JP-A-7-139539).
Further, in some cases, a plurality of circumferential grooves extending in a circumferential direction are formed in an inner circumferential surface of a half bearing that constitutes a plain bearing. Generally, such circumferential grooves are formed to enhance retainability of lubricating oil in the inner circumferential surface of the half bearing.
However, in recent years, an oil pump has been reduced in size in an internal combustion engine, and thus an amount of lubricating oil supplied to the inner circumferential surface of a bearing has been decreasing. Accordingly, when assembling a pair of half bearings into a cylindrical shape, if the circumferential end surfaces thereof are misaligned, the inner circumferential surfaces of the bearings come into direct contact with a surface of a shaft, and damage to the inner circumferential surfaces of the bearings is likely to occur due to the heat.
Therefore, it is an object of the present invention to provide a half bearing that is less likely to be damaged even if circumferential end surfaces are misaligned when assembling a pair of half bearings into a cylindrical shape and to provide a plain bearing formed by assembling such half bearings into a cylindrical shape.